Arc Welding Power Supplies : Arc Welding Power Supplies Arc Welding Power Supplies : 2 Arc Welding Power Supplies The current for arc welder can be supplied by line current or by an Alternator/generator.
The amount of heat is determined by the current flow (amps)
The ease of starting and harshness of the arc is determined by the electrical potential (volts).
Welding current adjustments can include:
High frequency current
Wave form Arc Welding Power Supplies : 3 Arc Welding Power Supplies The type of current and the polarity of the welding current are one of the differences between arc welding processes.
SMAW Constant current (CC), AC, DC+ or DC-
GMAW Constant voltage (CV) DC+ or DC-
GTAW Constant Current (CC) ), AC, DC+ or DC-
SAW CC/CV Slide 4: Welding Transformer and controls 400A 0-400A Moving coil
Magnetic amplifier control
Solid state controls
Wave form control Welding Generators : Welding Generators Twelve (12) Considerations When Selecting An Arc Welding Power Supply : 6 Twelve (12) Considerations When Selecting An Arc Welding Power Supply Maximum Amperage
Amperage adjustment mechanism
Input power requirements
Initial cost and operating cost
Size and portability Future needs for a power supply
Open circuit voltage 1: Amperage Output : 7 1: Amperage Output The maximum output of the power supply determines the thickness of metal that can be welded before joint beveling is required.
185 to 225 amps is a common size.
For an individual weld, the optimum output amperage is determined by the thickness of the metal, the type of joint and type of electrode. 2: Duty cycle : 2: Duty cycle The amount of continuous welding time a power supply can be used is determined by the duty cycle of the power supply.
Duty cycle may be 100%, but usually is less.
Duty cycle is based on a 10 minute interval.
Many power supplies have a sloping duty cycle.
Note in the picture there is a circle around the 75 amp setting. Why is it there? 8 What is the most likely outcome of exceeding a power supply duty cycle? Five Common Output Currents For Arc Welding : 9 Five Common Output Currents For Arc Welding 1. AC (Alternating Current)
2. DC (Direct Current)
3. ACHF (Alternating Current-High Frequency)
4. PC (Pulsed Current)
5. Square wave Arc Welding Electrical Terms : 10 Arc Welding Electrical Terms Electrical Circuit
Direct current (DC)
Alternating current (AC)
Ohms Law Constant potential
Open circuit voltage
Polarity To understand how an electric arc welder works, you must understand the following thirteen (13) electrical terms. Electrical Circuit : 11 Electrical Circuit An electrical circuit is a complete path for electricity.
Establishing an arc completes an electric circuit . Alternating Current : 12 Alternating Current Alternating current: The type of current where the flow of electrons reverses direction (polarity) at regular intervals.
Recommended current for SMAW general purpose electrodes and flat position. Direct Current : 13 Direct Current Direct current: The type of current where the flow of electrons (polarity) is in one direction.
Controlling the polarity allows the welder to influence the location of the heat.
When the electrode is positive (+) DCRP or DCEP it will be slightly hotter than the base metal. When the base metal is positive (+), DCSP or DCEN, the base metal will be slightly hotter than the electrode.
DC current is required for GMAW
It is frequently used for SMAW Ampere : 14 Ampere Amperes: the unit of measure for current flow.
Electricity passing through a resistance causes heat.
An air gap is a high resistance The greater the amperage flowing through the resistance (air gap)--the greater the heat.
The electrode also has resistance.
Excessive amperage for the diameter of the electrode (current density) over heats the electrode.
Insufficient amperage for the diameter of electrode makes the electrode hard to start. What are the characteristics of an electrode that was used with excessive current density? Voltage : 15 Voltage Voltage is the measure of electromotive force (Emf).
Emf is measured in units of volts
The voltage at the electrode for SMAW determines the ease of starting and the harshness of the arc.
Higher voltage = easier starting.
Starting voltage is called OCV. Voltage is adjustable in dual control SMAW machines.
Changing the voltage adjusts a GMAW machine for different metal thickness. Resistance : 16 Resistance Def: that characteristic of a material that impedes the flow of an electrical current.
Measured in units of Ohm’s ( )
When an electrical current passes through a resistance heat (BTU) is produced.
The amount of heat produced is a function of the amount of resistance (Ohm’s) and the amount of current (amps). Is the resistance adjustable in the SMAW process? Ohm’s Law : 17 Ohm’s Law Ohm's law states that, in an electrical circuit, the current passing through a material is directly proportional to the potential difference.
Commonly expressed as: Ohm’s law also be used to teach a principle of electrical safety.
Amperage is the harmful portion of electrical current.
Rearranging Ohm’s Law for amperage shows that amperage (current flow) is determined by the voltage divided by the resistance.
The higher the resistance, the less current that will flow for a given voltage. What does this principle mean for SMAW? Constant Current : 18 Constant Current In the normal operation of a transformer as amperage is increased, the voltage decreases, and vies versa.
Electrical arc welding power supplies are modified so that either the voltage or the amperage is relatively constant as the other factor changes. This allows two different types of power supplies:
In a constant current power supply, the current (amperage) stays relatively constant when the voltage is changed.
In a constant potential power supply, the voltage stays relatively constant when the amperage is changed.
SMAW Constant Current : 19 Constant Current Characteristics of constant current power supply.
The machine provides a high voltage for striking the arc.
Open circuit voltage (OCV)
OCV is not adjustable for most machines
When the arc is struck the voltage drops to the welding voltage.
Arc voltage varies with the arc length.
As the welding proceeds the current will not vary much as the arc length changes. Constant Current : 20 Constant Current Increasing the voltage from 20 to 25 volts (25%) only decreases the amperage from 113 to 120 Amp (5.8%). Constant Potential : 21 Constant Potential The constant potential power supply is modified to produce a relatively constant voltage as the amperage changes. Characteristic of GMAW power supplies. Voltage Drop : 22 Voltage Drop Voltage drop is the reduction in voltage in an electrical circuit between the source and the load.
Primary cause is resistance.
When an excessive voltage drop exists, the electrical circuit will not perform as designed.
Localized resistance (connection) can cause excessive heat.
Excessive heat can cause component failure.
When extra long welding leads are used, the amperage must be increased to have the same heat at the weld. Slide 23: Thyristor Rectifier
Available at 300A,400A 300A/
400A Slide 24: INVERTER POWER SOURCE HFAC Tr
20-80kHz AC-50Hz DC DC Slide 25: Size Reduction of Welding Tr. due to inverter HF Inverter Tr Slide 26: Welding Transformer – 200Kg Inverter based Unit - 20Kg Transformer Slide 27: Insulated Gate Bipolar Transistor(IGBT),
150A, 4.2kg suitable for MMAW & TIG
Consumption:3.7kVA, Cost: Rs.40,000 Slide 28: Ergonomic design – portability even at heights-
Suitable for construction sites Slide 29: Inverter Based MMAW
135 AMPS, 4.8 Kg Caddy PS PS Energy Efficiency : Energy Efficiency OUTPUT POWER INPUT POWER
Welding Transformer 6kW 12kW
Welding Generator 6kW 10kW
Transformer-Rectifier 6kW 9kW
Thyristor-Rectifier 6kW 8kW
Transistor controlled PS 6kW 7kW
Inverter Based PS 6kW 6.2kW Slide 31: GAS Metal Arc Welding Process Details Slide 32: MIG Welding system Slide 34: SAW
systems Slide 35: Lincoln Power wave AC/DC1000 Slide 36: Creep Start Slide 37: Hot Start Hot start / Soft start : Hot start / Soft start Start of welding on high wire feed speed ( > 23,0 m/min ) needs special characteristics
Soft start function allows to start welding with lower welding power to minimize unstable arc and wire feeding in start
Hot start function allows to pre heat thick base material effectively in arc ignition power can also be set higher than actual welding power
Adjustment range of function in SETUP is - 50% to 70% of welding power
If Soft start is -30%, welding power 10,0 m/min Soft start welding power 7,0 m/min
Before arc start Creep start slows wire feed speed to improve ignition
Hot / Soft start function is working on 2T / 4T trigger function and in Synercig control
At the end of welding crater filler function eliminate ending failures from weld Slide 39: Slope set up Slide 40: Double Pulse Arc dynamic regulation : Arc dynamic regulation By the arc dynamic regulation is influenced to the stability of welding arc in short arc.
The current rising angle and height determines the roughness of the arc, it can vary from soft to rough.
Arc dynamic regulation is operating automatic in Synercig control Soft arc ( -1….-9 )
decreases amount of spatters
welding with mix gases ( Ar / CO2 )
for Aluminium and Stainless steel alloys
welding with high parameters Rough arc ( 1….9 )
welding with CO2 gas
welding mild steel and thin plates with low parameters Basic setting ( 0 )
recommended basic setting